Solid-state circuits typically include transistors or other active devices that are mounted to printed wiring board (PWB) assemblies. In a typical configuration, a PWB assembly is formed by bonding a pallet to the bottom surface of a printed wiring board. The pallet acts as a heat sink to draw heat from the transistors and related componentry, a circuit to ground, and a structural support for the PWB.
The printed wiring board is generally provided with an opening that is aligned with a corresponding pocket formed in the pallet. The transistor is positioned in the pocket and protrudes through the opening in the PWB. The transistor leads are connected to the PWB, and the bottom of the transistor casing is coupled to the pallet.
A permanent warpage or bending of the newly formed PWB assembly can occur as the composite structure cools to normal operating or room temperatures. The warpage typically occurs in PWB assemblies having a significant size, wherein the various materials used in constructing the PWB assembly have differing coefficients of thermal expansion (CTE). The magnitude of the warpage can be severe enough to impede the process of bonding components to the PWB assembly and render ineffective conventional techniques used to transfer the dissipated heat from the operating electronic assembly to an attached heat sink.
Accordingly, improved constructions and methods of forming printed wiring board assemblies are desirable.